The work outlined in this proposal involves the genetic and molecular characterizations of glucuronidase structure and regulation in the mouse, Mus musculus. Genetic variation of glucuronidase structure has been observed among inbred strains in the form of three different allozyme forms. Variations in kidney androgen induction of enzyme activity has also been observed among these strains that segregates as a single gene closely linked to the structural locus. Additional genetic variation in glucuronidase structure and regulation has been formed in surveys of several sources of wild derived stocks of Mus musculus. Several of these genetic variants have been incorporated into the laboratory either as newly derived inbred strains or as congenic stocks carrying the new (Gus) complex on a common C57BL/6 background. In the coming year we will continue without characterization of new allelic structures using electrophoresis, isoelectric focusing, heat inactivation and antibody titration techniques. New regulatory alleles will be characterized by changes in enzyme activity following androgen induction, determination of relative rates of synthesis and by estimations of mRNA activity. Additional sampling of diverse populations of Mus musculus and closely related species and subspecies is planned to search for additional alleles of elements of the (Gus) complex as well as different haplotype combination of structural and regulatory alleles.